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排序方式: 共有696条查询结果,搜索用时 171 毫秒
391.
轻型载货汽车传动系参数的优化 总被引:1,自引:0,他引:1
根据轻型载货汽车的使用特点,在考虑了载荷工况对整车动力性、经济性影响的基础上,建立了轻型载货汽车传动系参数优化匹配的数学模型。选用约束变尺度方法,对某轻型柴油载货汽车传动系参数进行了多方案匹配优化,并给出了优化结果和试验结果,从而证明了该方法的实用性。 相似文献
392.
北京直径线盾构施工的关键技术 总被引:1,自引:1,他引:0
随着城市轨道交通事业的快速发展,盾构法施工技术在隧道建设中已得到广泛应用。结合北京站—北京西站地下直径线工程的盾构始发、盾构穿越护城河及下穿宣武门地铁站等施工实践,介绍在砂卵石地质条件下利用盾构法修建隧道的关键施工技术,以期为类似工程施工提供借鉴。 相似文献
393.
J. Piotrowski W. Kik 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2008,46(1):27-48
The presented model assumes semi-elliptical normal pressure distribution in the direction of rolling. The contact area is found by virtual penetration of wheel and rail. The normal pressure is calculated by satisfying contact conditions at the geometrical point of contact. The calculation is non-iterative, fast and completely reliable. It may be carried out on-line in MultiBody Systems (MBS) computer codes. The tests using the programme CONTACT by Kalker and experience from application in MBS codes show that the model is suitable for technical applications. The creep forces have been calculated with the FASTSIM algorithm, adapted for a non-elliptical contact area. Some applications in rail vehicle dynamics and wear simulation have been outlined. 相似文献
394.
Nong Zhang Guang-Ming Dong Hai-Ping Du 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2008,46(4):271-293
Vehicle rollovers may occur under steering-only maneuvers because of roll or yaw instability. In this paper, the modified fishhook and the sine maneuvers are used to investigate a vehicle's rollover resistance capability through simulation. A 9-degrees of freedom (DOF) vehicle model is first developed for the investigation. The vehicle model includes the roll, yaw, pitch, and bounce modes and passive independent suspensions. It is verified with the existing 3-DOF roll-yaw model. A rollover critical factor (RCF) quantifying a vehicle's rollover resistance capability is then constructed based on the static stability factor (SSF) and taking into account the influence of other key dynamic factors.
Simulation results show that the vehicle with certain parameters will rollover during the fishhook maneuver because of roll instability; however, the vehicle with increased suspension stiffness, which does not rollover during the fishhook maneuver, may exceed its rollover resistance limit because of yaw instability during the sine maneuver. Typically, rollover in the sine maneuver happens after several cycles.
It has been found that the proposed RCF well quantifies the rollover resistance capability of a vehicle for the two specified maneuvers. In general, the larger the RCF, the more kinetically stable is a vehicle. A vehicle becomes unstable when its RCF is less than zero. Detailed discussion on the effects of key vehicle system parameters and drive conditions on the RCF in the fishhook and the sine maneuver is presented in Part II of this study. 相似文献
Simulation results show that the vehicle with certain parameters will rollover during the fishhook maneuver because of roll instability; however, the vehicle with increased suspension stiffness, which does not rollover during the fishhook maneuver, may exceed its rollover resistance limit because of yaw instability during the sine maneuver. Typically, rollover in the sine maneuver happens after several cycles.
It has been found that the proposed RCF well quantifies the rollover resistance capability of a vehicle for the two specified maneuvers. In general, the larger the RCF, the more kinetically stable is a vehicle. A vehicle becomes unstable when its RCF is less than zero. Detailed discussion on the effects of key vehicle system parameters and drive conditions on the RCF in the fishhook and the sine maneuver is presented in Part II of this study. 相似文献
395.
396.
本文通过对轨道交通车站设备监控系统的研究,提出了轨道交通车站设备监控系统的研发方案,并对各子系统的功能进行了一定的阐述。 相似文献
397.
An analysis on long term emission benefits of a government vehicle fleet replacement plan in northern illinois 总被引:1,自引:1,他引:0
There have been a number of studies of the effectiveness of vehicle scrappage programs, which offer incentives to accelerated
scrappage of older vehicles often thought to be high emitters. These programs are voluntary and aimed at replacement of household
vehicles. In contrast, there is a gap in knowledge related to the emissions benefits of government fleet replacement (retirement)
programs. In this study, the efficacy of a fleet replacement program for a local government agency in Northern Illinois, the
Forest Preserve of DuPage County (FPDC), is examined using a probabilistic vehicle survival model that accounts for time-varying
covariates such as vehicle age and gasoline price. The vehicle lifetime operating emissions are calculated based on the estimated
vehicle survival probabilities from the survival model and compared with those derived using the EPA default fleet used in
MOBILE6 and the fleet represented by the Oak Ridge National Laboratory (ORNL) survival curve. The results suggest that while
there may be short term emission benefits of the FPDC fleet replacement plan, the long-term emission benefits are highly sensitive
to economic factors (e.g., future gasoline price) and exhibit a decreasing trend. This indicates that an adaptive multi-stage
replacement strategy as opposed to a fixed one is preferable to achieve optimal cost effectiveness.
Dr. Jie Lin (Jane) is an assistant professor in Department of Civil and Materials Engineering and a researcher with the Institute for Environmental Science and Policy at University of Illinois at Chicago. Her current research is focused on transportation sustainability through holistic modeling of energy consumption and emissions associated with private, freight, and public transportation activities. Dr. Cynthia Chen is an assistant professor in the civil engineering department at City College of New York. Her research expertise and interests cover travel behavior analysis, land use and transportation, transportation safety, and environmental analysis. Dr. Deb Niemeier is a professor at UC Davis and her current research focus is on the nexus between transportation, land use and climate change, particularly how land use and transportation decisions affect energy consumption and contribute to climate change. She is considered an expert on transportation-air quality modeling and policy and sustainability. 相似文献
Debbie A. NiemeierEmail: |
Dr. Jie Lin (Jane) is an assistant professor in Department of Civil and Materials Engineering and a researcher with the Institute for Environmental Science and Policy at University of Illinois at Chicago. Her current research is focused on transportation sustainability through holistic modeling of energy consumption and emissions associated with private, freight, and public transportation activities. Dr. Cynthia Chen is an assistant professor in the civil engineering department at City College of New York. Her research expertise and interests cover travel behavior analysis, land use and transportation, transportation safety, and environmental analysis. Dr. Deb Niemeier is a professor at UC Davis and her current research focus is on the nexus between transportation, land use and climate change, particularly how land use and transportation decisions affect energy consumption and contribute to climate change. She is considered an expert on transportation-air quality modeling and policy and sustainability. 相似文献
398.
基于SEM模型的轨道交通企业员工满意度评价 总被引:1,自引:0,他引:1
员工满意度的高低直接影响着企业经营活动的效率。本文首先介绍了结构方程模型(SEM模型)的基本原理,然后从轨道交通企业的特点出发,建立了轨道交通企业员工满意度评价的SEM模型及指标体系,最后以深圳地铁运营分公司员工满意度评价为例,对SEM模型进行了实证性研究。 相似文献
399.
文章分析了轨道交通客流需求量的影响因素,以拥挤条件下的出行阻抗函数为基础,通过引入弹性需求条件下的轨道交通均衡配流条件,构建了弹性需求的均衡配流模型。根据模型的特点,给出了改进的用于求解弹性需求下的轨道交通均衡配流模型的Frank-wolfe算法。最后通过一个算例说明了算法的有效性和合理性。 相似文献
400.
The workshop considered system development as a key element of improving the performance of public transport. The main theme was the governance of decision making, design and development of public transport projects. A first main finding is that governance should be improved to keep focus on the original values for which the projects are started. Many projects lose sight of their original aims through the long and often problematic process from inception to operation. A second main finding is that the technological choice, mainly between rubber on tarmac and steel on rails, can be postponed, as both technologies start to overlap in their capacities. A stronger focus on functional needs in the earlier phases of the projects could help. Finally, as the different technologies provide similar options and can be used interchangeably, communicating the service they provide in other ways then through vehicle and infrastructure technology becomes more important. 相似文献